1. Field of the Invention
The present invention relates to an irreversible circuit element such as a circulator, an isolator or the like which is used in an antenna multicoupler or the like.
2. Description of the Related Art
To explain the constitution of a conventional irreversible circuit element in conjunction with FIG. 8 and FIG. 9, an irreversible circuit element S2 is made up of a dielectric substrate 52 which includes three center conductors 51 formed of three metal plates which are arranged at an interval of 120 degrees and have portions thereof to cross each other and an insulation material which embeds these three center conductors 51 by molding, a magnet 53 which is arranged over the crossing portion of the center conductors 51, a circular ferrite plate 58 which is arranged below a crossing portion of the center conductors 51, a first yoke 54 which is formed of a magnetic plate and is arranged such that the first yoke 54 covers an outer portion of the magnet 53 disposed above the dielectric substrate 52, and a bottomed second yoke 55 which is connected to the first yoke 54, is made of a magnetic plate and is arranged such that the second yoke 55 covers an outside of the ferrite plate 58.
Further, in the irreversible circuit element S2, a magnetic closed circuit is formed of the first and second yokes 54, 55 and, at the same time, terminals 51a for inputting/outputting which are provided to three center conductors 51 are projected outside from sides of the first and second yokes 54, 55.
A printed circuit board 56 for an antenna multicoupler or the like is provided with a hole 56a and a plurality of conductive patterns 57 are formed on a periphery of the hole 56a. 
Further, on the printed circuit board 56 to which the conductive patterns 57 are applied, various electric components such as chip-type capacitors (not shown in the drawings) connected to the irreversible circuit element S2 are mounted thus forming a desired electronic circuit.
Further, the irreversible circuit element S2 is positioned in the hole 56a of the printed circuit board 56 and the terminals 51a of the center conductors 51 and ground electrodes not shown in the drawing are placed on the conductive patterns 57 and are connected to the conductive patterns 57 by soldering.
The conventional irreversible circuit element is configured such that the dielectric substrate 52 which embeds three center conductors 51 made of metal plates by molding and the ferrite plate 58 are overlapped to each other and hence, the irreversible circuit element exhibits the large thickness and there has been a drawback that the constitution is not suitable for reducing the thickness.
Further, since the capacitor connected to the irreversible circuit element S2 is mounted on the printed circuit board 56, there exists a drawback that not only a chip-type capacitor is necessary but also the printed circuit board 56 becomes large-sized.
Accordingly, it is an object of the present invention to provide a thin irreversible circuit element provided with capacitors.
As the first means to solve the above-mentioned drawbacks, an irreversible circuit element including a planar ferrite member, a plurality of dielectrics which are laminated to the ferrite member, the dielectrics being formed of an insulation material, and first, second and third center conductors which are formed on surfaces different in the vertical direction while sandwiching the dielectrics therebetween, the first, the second and the third center conductors having portions thereof to cross each other in the vertical direction.
As the second means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the first, the second and the third center conductors are formed on different surfaces of the dielectrics using conductive layers and, at the same time, the dielectrics have connection portions which are made of conductive layers which are respectively connected to the first, the second and the third center conductors.
As the third means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that a plurality of electrodes which face portions of the connection portions which are respectively connected to the first, the second and the third center conductors are provided to the dielectrics and/or the ferrite member, and a capacitor is formed between one portion of the connection portion and the electrode.
As the fourth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the plurality of electrodes formed of the conductive layers are formed on an upper surface of the ferrite member.
As the fifth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that a plurality of holes are formed in the dielectrics and the ferrite member, and one-end sides of the first, the second and the third center conductors are electrically led out to a lower surface of the ferrite member in a state that one end sides of the first, the second and the third center conductors are connected to connection conductors formed inside the holes.
As the sixth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the electrodes are connected to the connection conductors.
As the seventh means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that a lower electrode which is formed of a conductive layer is formed on a lower surface of the ferrite member and the connection conductors are connected to the lower electrode.
As the eighth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the connection portions which are connected to other-end sides of the first, the second and the third center conductors are electrically led out to a lower side of the ferrite member by way of the first conductor made of a conductive layer formed on a side face of the ferrite member.
As the ninth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that one-end sides of the electrodes are electrically led out to a lower side of the ferrite member by way of a second conductor which is formed of a conductive layer provided to a side face of the ferrite member.
As the tenth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the dielectrics are formed of insulation films.
As the eleventh means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the ferrite member is constituted of a block body which is formed by laminating a plurality of ferrite thin plates.
As the twelfth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the irreversible circuit element includes a magnet which is arranged over the dielectrics, a first yoke which is arranged to cover the magnet, and a second yoke which is arranged below the ferrite member, and wherein a magnetic closed loop is constituted of the first and the second yokes.
As the thirteenth means to solve the above-mentioned drawbacks, the irreversible circuit element is configured such that the second yoke is arranged in a recess formed below the ferrite member, the second yoke is formed below the ferrite member, and the second yoke is electrically bonded to a lower electrode which becomes conductive with one end sides of the first, the second and the third center conductors.